A Chemist's April Fools' Joke: Nitrogen Triiodide

I was recently asked about interesting chemical reactions and so I started thinking about a few fun demonstrations that we like to do during National Chemistry Week, or at the University's Open House. Which brought me to nitrogen triiodide.

Nitrogen triiodide (NI3) is a contact explosive. There are many types of explosions and explosive materials, but I will focus on chemical explosives. An explosion is characterised by the rapid increase in volume and release of energy. This is also accompanied by the production of heat, light, sound, and pressure (the shock wave-this is the part of an explosion that does the damage). Generally explosions produce gasses, this is because the production of gasses is an extremely thermodynamically favourable (see blog entry A Diamond is Forever...Or Maybe Not) process. Explosions are detonated by the application of energy. In the case of a contact explosive, only very small amounts of energy need to be applied to the material. This energy can be in the form of heat, light, sound, or physical pressure. 

Nitrogen triiodide is very sensitive as it produces nitrogen gas and iodine, which are way more stable compounds and therefore results in a huge release of energy. It also produces a sound reminiscent of a gunshot. It does, however, leave purple stains due to the iodine. This compound is actually so sensitive that brushing it lightly with a feather can cause an explosion. The sound produced by the explosion can actually cause subsequent explosions of the compound to occur. I think the following video shows it best:

http://www.youtube.com/watch?v=2KlAf936E90 

A great practical joke is to place this on the underside of toilet seats or in the key holes of doors. Small amounts of course. Just to scare people. (Please note: the author of this blog is not recommending that you try this at home.)